Sanitary napkin



Sept. 28, 1965 s, L. PORTER ETAL SANITARY NAPKIN Filed Feb. 26

Ulli d Sta P Q i 3,208,451 te Patented Sept. 28, 1965 other continuous lilamentary materials of comparable low 3,208,451 denier.

SANITARY NAPKIN Stephen L. Porter, Harrisonburg, and Calvin Auville, Dayton, Va., and Allen R. Winch, Westfield, NJ., assignors to Celanese Corporation of America, New York, N.Y., a corporation of Delaware Filed Feb. 26, 1959, Ser. No. 795,858 10 Claims. (Cl. 12S-290) The present invention relates to warp-knit fabrics.

It is an object of the present invention to provide fabrics which are soft, light in weight, strong and easy and inexpensive to produce.

It is a further object of the invention to provide a fabric having the properties described which conforms readily to contoured shapes without bunching or wrinkling.

Another object of the invention is to provide an open fabric which will permit the ready passage of liquid therethrough without excessive wicking.

Still another object of the invention is the provision of fabric coverings for sanitary napkins, for non-woven articles, of decorative ribbons, and the like.

Other objects and advantages of the invention will become apparent from the following detailed description and claims.

In accordance with one aspect of the invention there is provided a warp-knit fabric of open construction weighing less than about 1, and preferably less than about-0.8 ounce per square yard. The fabric is especially suited for use as the outer covering of sanitary napkins andrparticularly of contoured or. shaped sanitary napkins in which end use the ability of the fabric to conform without bunching and attendant discomfort is most advantageous.

For such end use, the fabric is preferably knit of continuous filament yarns since in that manner the necessary strength can be achieved at low deniers, low deniers being softest. The denier of the yarns generally is less than about 150 and perferably less than about 125 but usually at least l denier. Advantageously the 'fabric is knit on a double bar machine, the yarns of one bar forming longitudinally extending chains to lock the essentially transversely extending yarns of the other bar into predetermined position in forming the fabric. Because ofthe loopformation of the yarns in forming the chains, these chains exhibit increased strength and advantageously may be made of yarns of less than about 75 denier. The transversely extending yarns, however, while preferably below about 100 denier are dcsirably of somewhat higher denier than the chain yarns.

Advantageously the individual filaments of the yarns are less than about 2O and perferably less than about 5 denier since the lower deniers are softer. The chemical composition of the yarns may vary widely and, for example, may constitute rayon, nylon, polyesters such as polyethylene terephthalate, polymers and/or copolymers of olens or vinyls such as ethylene, proylene, vinyl chloride,

vinylidene chloride, acrylonitrile, and the like. Preferably, howevcr, the yarns comprise organic acid esters of cellulose such as the lower alkanoic acid esters, e.g. cellulose acetate. Cellulose acetate is desirable because of its softness, its inertness. and its balance of hydrophilic and hydrophobic properties, i.e. a material will not be suitable which is so hydrophobic as to resist penertation of aqueous fluids or so hydrophilic that it will wick up the fluid rather than permitting the fluid to pass into deeper layers of the napkin intended for absorbency.

Another advantage of cellulose acetate is that it can easily be adhered to the substrate without stitfening, e.g. as by spraying the substrate lightly with a solvent such as acetone, a ptasticizer such as triethyl citrate. or the like. Most important, cellulose acetate is less expensive than The fabric when used for sanitary napkins should have a pinning strength, defined more fully hereinafter, in ex- 5 cess of about 2 and perferably in excess of about 2.5 pounds. The pinning strength will depend upon the yarn denier and the fabric construction. A satisfactory construction has been found to involve yarns on one bar of a double bar warp-knitter which yarns span just one needle j() and form chains, e.g. the bar may be threaded l in 2 out and the stitch pattern will be l-G, 0l. The yarns of the other bar are the transversely extending yarns; these may span several needles and may be knotted to adjacent transversely extending yarns on one or both sides by the chain yarns of the first bar. This, of course, will depend upon the threading and stitch pattern. Alternatively, each of the transversely extending yarns may be knotted to only chain yarn and to no adjacent transversely extending yarn, being merely looped, not positively knotted to adjacent transversely extending yarns; this makes for more rapid machine operation and for production of a softer fabric still exhibiting adequate strength.

Where multifilament yarns are employed the filaments are generally twisted together to permit processing on the knitting machine. Advantageously there are l0 or fewer turns per inch and preferably l or fewer turns per inch since low twist yarns, while less expensive, give softer fabrics and more cover than high twist yarns.

In addition to their use as coverings for sanitary nap-V kins, the novel fabrics can be employed wherever low weight fabrics are desired. Thus they can constitute a backing or scrim in place of gauze for non-wovens such as filters, battings used in making quilted fabrics, and the like. Alternatively, they may be made innarrow widths and used as decorative lace-work ribbons alone or in conjunction with plastic lms, etc.

In connection with variations in the width of the fabric in end use applications, the use of warp-knit fabrics presents certain additional advantages. Thus the knitting machine may be made to produce, in full width and by appropriate omission of certain warp yarns several fabrics of less than full machine width may be simultaneously produced. As compared with having to produce narrower widths by cutting a wide fabric, the invention avoids uneven edges With fiber strands and shreds. Alternatively, the fabric may be produced in full widths and by absence of locking between adjacent warps it may neatly be subdivided into several fabrics of lesser width.

As contrasted with circular knit fabrics, the warp knit j fabrics are free from curling at the edges and they arev easily handled dur-ing wrapping about the napkin paddue to-their low stretch in longitudinal direction. The high stretch in the transverse direction still permits the wrinklefree accommodation to various shaped articles with good contact between the fabric and article, desirable in per- -mitting capillary flow through to the article.

The novel fabrics properties cannot be duplicated by weaving. Thus continuous filament 'yarns when woven tend to slide over one another, especially when subjected to stress as in pulling on a pin, and result in a dimensionally unstable fabric.- This sliding tendency can be overcome by bonding but this stiffens the fabric rendering it uncomfortable. If staple -ber yarns are substituted for continuous filament yarns, the lesser strength will necessitate the use of heavierdenierscoarser yarns and coarser constructions.

The invention will be further described with reference to the accompanyind drawings, wherein:

FIG. l is a diagrammatic illustration of the construction one fabric; y

FIG. 2 is a diagrammatic illustration ofthe construction of a second fabric; and

FIG. 3 is an elevation of a sanitary napkin immediately prior to wrapping of the cover layer thereabout.

Referring now more particularly to the drawings, in FIG. 1 there is shown a fabric comprising warp yarns 11 formed into longitudinally extending chains and other warp yarns 12 formed into essentially transversely extending yarns. The dots 13 represent the needle positions and from the figure it can be seen that the bar carrying yarns l1 is threaded l in 2 out with a 1 0, 0-1 stitch pattern while the bar carrying yarns 12 is threaded l in l out f1 in 3 out with a 0-0, 5-5 stitch pattern.

In the fabric illustrated in FIG. 2, the positions of needles 14 show that the bar carrying chainsforming warp yarns 15 is threaded 1 in 2 out with a l-0, 0-1 stitch pattern while the bar carrying transversely extending warp yarns 16 is threaded l in 2 out with a stitch pattern of 3-4, 1-0. It will be seen that the laterally projecting loops of each wale are not knotted to the projecting loops of adjacent wales; instead the loops of each wale fit loosely into the adjacent loop (not shown, but apparent from the shorthand illustration). Consequently the wales can be separated from one another, if desired, to produce fabrics of predetermined width. Advantageously, at least every twentieth, e.g. every tenth transverse yarn is not knotted to one of the adjacent transverse yarns or every single transverse yarn is not knotted 4o both of the adjacent yarns Thus the chain yarn bar was threaded 2 in 2 out-l in 2 out (71 times)l in 3 out 2 in l out, starting with the first guide on the bar. The back bar was also threaded starting with the first guide, 1 in 2 out (74 times-Z out. This produced a 7 inch wide fabric with selvages, making a nearer appearing fabric. In addition it eliminated break-outs which otherwise occurred at the edges, and thereby increased the production speed. In other re` spects the fabric was the same as that produced in Example l.

The products of Examples l and l0 are all-around the best from the standpoints of low weight, high pinning strength, softness, satisfactory appearance and balance between hydrophobic and hydrophilic properties. The fabrics provide sufficient cover for the encased layers so as not to appear too flimsy; at the same time even though the cover layers exert no action on fluids placed thereon they are sufficiently open and have many pores of adequate size to permit viscous fluids to be wicked up by the substrata of the napkins.

It is to be understood that the foregoing detailed description is merely given by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to .Msecure by Letters Patent is:

(FIG. 2) so as to permit severing into fabrics of whatever width desired. Alternatively by omission of selected warp yarns severalfabrics of predetermined width can be simultaneously -produced without slitting.

FIG. 3 shows the stackedpad layers plus cover layer for forming a sanitary napkin. The layers comprise three sheets of tissue paper 17, a web of viscose liber 18, two sheets of tissue paper 19, a layer of wood pulp fiber 20, a sheet of water repellent tissue 21, four sheets of tissue 22, another layer of wood pulp fiber 23, another sheet of tissue 24, eight sheets of tissue 25 and a cover layer 26. ln accordance with the present invention this cover layer 26 is constituted by a warp knit fabric of the construction shown in FIGS. l and 2.

The following table illustrates several satisfactory fabric construction, employing cellulose acetate continuous -iament yarns twisted to the extent of about l turn per inch:

l. A sanitary napkin comprising an absorbent pad and a fabric covering said pad, said fabric being warp-knit of a plurality of sets of continuous lament cellulose aeetate yarns of about l0 to about 150 denier into an open construction which imparts thereto a low stretch walewise and a high stretch course-wise and weighing less than about l ounce per square yard, each of said sets comprising a plurality of yarns.

2. A sanitary napkin comprising an absorbent pad and a fabric covering said pad, said fabric being warp-knit of sets of continuous filament yarns of two dierent deniers each of said sets comprising a plurality of yarns, the yarns of one of the sets having a denier of about 10 to about 100 and the yarns of the other set having a denier of less than about 75, said yarns being knit into an open construction which imparts to said fabric a low stretch Wale-wise and a high stretch course-wise and a weight of less than about one ounce per square yard.

EXAMPLE N 0 l 2 3 4 5 6 7 8 9 Stitch pst Fig 2 2 2 1 2 l 1 l Chain yarns, enisr/ills ilo/22 Bil/22 ile/'22 [22 155/22 55/22 65/15 5.5/16 55/15 Transverse yarns, dcnier/flls---. 75/20 75150 'I5/60 75/60 75/'250 I5/20 56/15 715/20 55/15 Wales/inch 2l 21 28 28 28 28 23 28 28 Courses/inch 11 23 28 23 28 Y 2l 28 44 Fabric weight, ounces/sq. yd.-.. 0. 64 0. 67 0. 67 0. B 0. 67 0. 8 0. 67 0. B 0. u inches/rack (480 courses 28 21 21 17 2l 17 23 17 l1 Inches o( chain yarns fed/rack... 94 'I0 70 00 70 60 74 64 58 Inches oi transverse ,uns lsd/ ruck m 100 100 46 l 4d 1m 48 44 Plnniug strength, lbs- 8. 6 3. 5 8. l 2. 8 2. 4

The pinning strength was determined by clamping one end of a fabric sample between a pair of jaws mounted at a xed location on a rod. Another pair of jaws was mounted on a carriage capable of sliding along the rod; the second pair of jaws had two -L-shaped pins projecting therefrom and spaced one-half inch laterally from one another. The pins extended toward the tirst pair of jaws and then stuck up through the fabric. A weight was mounted on the second pair of jaws and the rod was tilted to vary the tension on the fabric, the fabric wales running parallel to the rod. The pinning strength is the vector of the weight acting along the rod when the pins tore the fabric. Any other tensile testing machine meeting ASTM D-76-53 requirements, suitably modified with pins, can be similarly employed.

EXAMPLE l0 Another sample was prepared generally similar to Sample 1 but differing therefrom in the stitch pattern.

3. A sanitary napkin comprising an absorbent pad and a continuous filament warp-knit fabric covering said pad, said fabric comprising a plurality of longitudinally extending chain yarns holding together a plurality of essentially transversely extending yarns, the chain yarns having a denier lower thanthe transversely extending yarns, said yarns being knit into an open construction which imparts to said fabric a low streach wale-wise and a high stretch course-wise and a weight of less than about one ounce per square yard.

4. A sanitaryv napkin comprising an absorbent pad and a fabric covering said pad, said fabric being warpltnit of two seta of continuous cellulose acetate filaments, one set comprising a plunality of yarns having a denier of about l0 to about 75, a stitch pattern of l-0, 0-1 and a threading of l in 2 out, the other set comprising a plurality of yarns having a denier of about l0 to about 100 and a stitch pattern several needle spaces wide, said yarns being knit into an open construction which imparts to said fabric a low stretch wale-wise and a high stretch coursewise, a weight of less than about l ounce per square yard and a pinning strength in excess of about 2 pounds.

5. A sanitary napkin comprising an absorbent pad and a fabric covering said pad, said fabric being warp-knit of two sets of continuous filament yarns, each said sets comprising a plurality of yarns, the yarns of one set having a denier of about to about 75 and a stitch pattern of 1-0, 0-1, the yarns of the other set having a denier of about l0 to about 100 and a stitch pattern several needle spaces wide, said fabric being knit into an open construction which imparts to said fabric a low stretch Wale-wise and a high stretch course-wise, a weight of less than about 1 ounce per square yard and a pinning strength in excess of about 2 pounds.

6. A sanitary napkin comprising an absorbent pad and a fabric covering said pad, said fabric comprising a plurality of sets of continuous lament yarns wrap-knit into an open construction which imparts to said fabric a low stretch Wale-wise and a high stretch course-wise and a weight of less than about 1 ounce per square yard, each of said sets comprising a plurality of yarns.

7. A sanitary napkin comprising an absorbent pad and a fabric covering said pad, said fabric being warp-knit of a plurality of sets of continuous lament yarns of about l0 to about 150 denier into an open construction which imparts to said fabric a low stretch Wale-wise and a high stretch course-wise and a weight of less than about l ounce per square yard, each of said sets comprising a plurality of yarns. v

8. A sanitary napkin comprising an absorbent pad and a fabric covering said pad, said fabric being warp-knit of two sets of continuous filament yarns, each of said sets comprising a plurality of yarns, the yarns of one set having a denier of about 10 to about 75 and a stitch patternof 1-0, 0 1, the yarns of the other set having a denier of about 10 to about 100 and a stitch pattern several needle spaces wide, said yarns being knit into an open construction which imparts to said fabric a low stretch Walewise and a high stretch course-wise, a weight of less than about 1 ounce per square yard and a pinning strength n excess of about 2 pounds. t

9. A sanitary napkin comprising an absorbent pad and a fabric covering said pad, said fabric being of open construction, weighing less than about 1 ounce per square yard and being warp-knit from two sets of continuous filament cellulose acetate yarns, the yarns of one set having a denier of less than about and a stitch pattern of 1-0, 0-1, and the yarns of the other set having a denier of less than about 100, a stitch pattern of O-O, 5-5 and a threading of 1 in 1 out 1 in 3 out.

10. A sanitary napkin comprising an absorbent pad and a fabric covering said pad, said fabric being of open construction, wcighing less than about 1 ounce per square yard and being warp-knit from two sets of continuous filament yarns, each of said sets comprising a plurality of yarns, the yarns of one set having a denier of about l0 to about 75 and a stitch pattern of 1-0, 0-1, and the yarns ofthe other set having a denier of about l0 to about l00'and a stitch pattern several needle spaces wide.

References Cited bythe Examiner UNITED STATES PATENTS OTHER REFERENCES Tricot Fabric Design, by T. H. Johnson, published by McGraw-Hill, New York, N Y. copyright 1946,'pages 77 and 78.

RICHARD A. GAUDET, Primary Examiner.

JORDAN FRANKLIN, R. I. HOFFMAN, R. C.

MADER, J. R. KLINE, Examiners. 

1. A SANITARY NAPKIN COMPRISING AN ABSORBENT PAD AND A FABRIC COVERING SAID PAD, SAID FABRIC BEING WARP-KNIT OF A PLURALITY OF SETS OF CONTINUOUS FILAMENT CELLULOSE ACETATE YARNS OF ABOUT 10 TO ABOUT 150 DENIER INTO AN OPEN CONSTRUCTION WHICH IMPARTS THERETO A LOW STRETCH WALE- 